<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.5.17/dist/vue.js"></script>
    <style>
        .color {
            color: red;
        }
        .bg {
            background: pink;
        }
        .border {
            border: 1px dotted #000000;

        }
    </style>
</head>
<body>
    <div id="app">
        <h1 :class="[color,isActivity?bg:border]">这是一级标题</h1>
        <button @click="isActivity=!isActivity">更换</button>
    </div>
</body>
<script>
    const app = new Vue({
        el: '#app',
        data:{
            color: 'color',
            bg: 'bg',
            border: 'border',
            isActivity: true
        }
    })
</script>
</html>